A driver has an ability to recognize a surrounding situation of a vehicle, but when the driver repeatedly drives, his/her concentration falls. When the driver's concentration falls, the driver cannot unconsciously recognize a movement of his/her vehicle. In this situation, the driver cannot recognize a dangerous situation, so that an accident occurrence probability is high. Particularly, an accident occurrence probability by a driver, who is insensitive to a change in a surrounding environment of a vehicle, is higher.
In order to alleviate the problem, an assistance system capable of assisting driving is mounted in a vehicle, and examples thereof include a lane departure warning system (LDWS) and a lane keeping assistance system (LKAS).
As is well known, the LDWS is a system warning a driver of a lane departure situation of a vehicle, and notifies a driver of a dangerous situation of a vehicle only when the vehicle deviates a lane without considering a movement of the vehicle occurring in a situation where the driver cannot recognize the dangerous situation, so that the LDWS is not a solution capable of fundamentally solving the aforementioned problem.
The LKAS is a system for automatically controlling a driving direction (or a travel direction) of a vehicle into an inner side of a lane when the vehicle deviates from the lane, but is stably operated only when a movement of the vehicle is normal, so that the LKAS cannot prevent an accident from occurring in an abnormal situation.